Strand treating apparatus



Feb. 8, 1944. P KNAUS STRAND TREATING APPARATUS Filed D80. 30, 1941 Patented Feb. 8, 1944 UNITED STATES PATENT oEElcE STRAND TREATING APPARATUS Peter J. Knaus, Hinsdale, Ill., assignor to Western Incorporated, New York, N. Y., a corporation of New York Application December 30, 1941, Serial Nm-42L843 1 invention may be embodied by providing an Electric Company,

Claims.

This invention relates to strand treating apparatus, and more particularly to apparatus for coating strands.

Insulating sheathings on electrical conductors are made in many ways, some of which include the application of hardenable materials applied in liquid,- semi-liquid, or pasty form and subsequently hardened to a bare or previously sheathed strand. Thus materials in the nature of paint, enamel, varnish, or waxes, asphalts, paraflins and the likedissolved in volatile vehicles, artificial resins hardenable by polymerization induced by heat, and other analogous materials, are used for one or another specific purpose. such instances a solvent or vehicle is used which is volatilized and is subsequently recovered; a considerable part of the cost of the coating operation may arise out of the volume of such solvent or vehicle to be recovered for subsequent re-use.

Hence it is desirable to apply the raw sheathing or sheath treating materials as a smoothly plastic highly viscous paste, in order that the volume of vehicle or solvent circulated in the process, or perhaps wasted, may be kept low.

In coating or impregnating previouslycovered wire strands with cellulose acetate considerable In many a a u a y comprising a chambered body to contain the material and formed with entrance. and, exit apertures to support the dies used,means to coat the strand including a die of resilient material having an aperture' 'therethrough of approximately the diameter of the strand, the die being so formed as to have a deep annular groove in its side surfacesand the lower-portion or the die cut out in part to permit the coating material to reach the grooved portion so as to exert a pressure'thereon. By using a die of shape the v coating-material passes freely through the openings in the lower press on the narrowed'p'jortionof the die. Since the pressure'exerted on this portion or the die tendency for the material to escape, will, in short, compression or the die v diiiiculty has been experienced in providing a die that will both produce an even coating "and pre vent escape of. the coating material from the coating chamber. Variations'in the size of the strand require an aperture capable of dilating to permit passage. The pressure of the coating material on the other hand requires that the aperture be fitted tightly enough to permit only sumcient material to pass with the wire to satisiactorily coat the same. Rubber corks such as used' for bottle stoppers have been provided with a hole in the center for the wire to pass through but with ordinary stopper-shaped dies no compensation is possible for variations in the pressure of the coating material.

Also in previously used rubber dies considerable difliculty has been had from popping." "Pop- I out of the die,

-metal caps l6, l1, l8 and will be about the same asthe pressure exerted at the die aperture, the tendency of the coating material to force its way out through the die will be compensated by the compression of the walls of the die by the coating material. Any increase in pressure, and consequently an increase in the result in commensurate walls. This has been found to adequately compensate "for changes'in pressure:

Other objects and advantages will appear irom the following detailed description of one embodi ment of the invention taken in connection with the accompanying drawing wherein:

Fig. 1 is a view in'vertical transverse central section of an apparatus constructed in accordance with the invention.

Fig. 2 is a central section of the left hand die of Fig. 1.

Fig. 3 is a plan view of In the embodiment of this invention shown on the accompanying drawing a metal casing Hi is shown having apertures H, l2, l3 and H suitably spaced therein. The walls I! of saidiapertures are extended at right angles to'the casing a suitable distance and threaded to receive threaded apertures II and II are sonically shaped to receive dies 29 and 30. The lower caps I8 and I! are so designed that a portion 25 forms an inlet die integrally therewith and extends into the apertures l3 and Min is'apertured at 26 to permit free passage of a strand 21. Thus these lower caps and their integral dies act as guides for the strand. The p strand initially passes through dies 28 and I0 and then after the coating has been hardened by suitable means the coated strand-is'passed,

coating material to a strand part0: the die and is able to for coating strands and the die shown in Fie. 2.

IS. The upper, the exit,

the-casing. This portion through dies 26 and 29. The speed with which the strand may be drawn through the apparatus is preferably in excess of 1,200 feet per minute and at this speed any coating material which might tend to extrude through the lower dies is largely returned at once. Since the strand is nearly dry and, therefore, unlubricated when it reaches the lower caps it is necessary in order to reduce friction to use apertures in the caps substantially greater in diameter than the size of the strand with which they are to be used. Satisfactory results have been obtained with a passage of .125" when using a wire of .046" in diameter.

The casing I is filled with coating material under a pressure of from 60 to 80 pounds per square inch. Coating material of a viscosity of 25,000 poises at 75 Fahrenheit works satisfactorily Means for introducing the material into the chamber and maintaining pressure thereon are conventional and well known to the art, and therefore are not shown. Means, of course, are also provided for feeding the strand and pulling it through the machine. These means are conventional and are not shown. Means such as disclosed in the patent to E. E; Newton :et a1. 2,260,860 and the patent to F. R. Reevely 2,218,482 may be employe Figs. 2 and 3 show the rubber die 30 having a deep groove 3| which extends annularly around the outside of the die. The lower portion 32 of the die 30 is cut away segmentally forming a spider shaped head to permit free access of the coating material to a center portion 33 of the die, the purpose being to permit the coating material to exert pressure on this center portion. Enough of the lower portion of the die is left to provide support for the die. The upper portion 34 is solid and disc shaped to prevent escape of coating material. 35 of about the same size as the strand with which the die is to be used The exit and entrance of this passage are chamfered to prevent popping."

The die 29 is also made of rubber and is of frusto conical shape. A passage 36 is provided through the center of the die of about the same size as the strand with which the die is to be used. The exit and entrance of this passage are chamfered to prevent "popping." This die is used to produce a final finish on the strand.

It is the particular purpose of the presentinvention to make a strand having a coating of thick pasty, almost solid, viscous material, 5 or 6 times as thick as that which can be applied on a strand by the relatively thin coating materials heretofore used? This is highly advantageous because the number of coating passes of the strand, therefore, is cut to of those heretofore required to produce coats of like final thickness. Also the volume of solvent required to be evaporated off and either wasted or expensively recovered is very materially lessened and hence a considerable savings is effected in the cost of the whole operation.

In accordance with the present invention a coating material may be used which contains 58% by weight of solids, largely cellulose acetate and 42% by weight of a liquid solvent, largely acetone. The viscosity of this is about 25,000 poises at 75 Fahrenheit, and at the extrusion temperature of about 105 poises.

/5 or Vs the number In using the device above described for coating a strand, comprising textile thread served on number 22 wire with the coating preparation above described, the strand 2! is drawn from some suitable supply and is threaded through the passage 26 in the cap I8. The strand is then led across the chamber and thus through the coating material thereon and then out through the rubber die 30. Then the wire passes through suitable means to partially or wholly harden the coating. These means are not shown as they form no part of the present invention. About 50 mgs. of coating material per linear foot are extruded onto the wire inthis first pass. The once coated strand is then, as aforesaid, subjected to a hardening operation and then returns to pass upwardly through the cap is and then through the wiping die 29. About 20 mgs. of coating material per linear foot are extruded onto the wire in this pass. A range of from 60 to 90 mgs. per linear foot is used, about 70 mgs. of coating material per linear foot being optimum. The cellulose acetate material being under pressure of from 60 to pounds per square inch forms on the strand and is wiped smooth by the dies 29 and 30. A coating of suitable thickness remains on the wire as it emerges from the dies, the thickness being controlled by the size of the bores 35 and 36 and by'the' hardness of the rubber dies 29 and 30 and by the pressure of the coating material.

As is well known there will, of course, be irregularities in the diameter of the strand, the most frequent cause of'such irregularities is splices in the wire or knots in the textile threads served on the wire core. Therefore a die must be used which is resilient. Rubber seems ideally suited to this need; however, dies niade of other suitable resilient materials such as neoprene will work equally well. Resilient materials having a hardness rating of between 30 and 70 on a have-been foiind to work satis- Shore Durometer factorily. I v a The particular design of the die 30 permits considerable distortion inaddition to the inherent distortability of the rubber. This has been found to be necessary for the first pass. However, the strand having once 'been coated and passed through die 30, it has been found to be sufliciently uniform to pass satisfactorily through the die 29. although the die 29 has no special configurations to facilitate dilation or distortion. 1

The embodiments of herein described are merely illustrative and may 2. In a strand coating apparatus, an extrusion chamber to receive plastic coating 3. In an apparatus for coating strand material,

an extrusion chamber, a guiding die in one side of said chamber, means for supplying coating material to said chamber, and an extrusion die of resilient material in the opposite side of said chamber, said extrusion die having a head, a redie having a head, a reduced center portion and [a ,spider' shaped base comprising a plurality of radially extending-fingers, and the outlet apertureof said die being an I chamfered to obtain smooth coating 0! the strand.

5. In an ap aratusforlcoating strand material,

duced center portion, and a spider shaped loa'se comprising a plurality of radially extending fingets, the outlet aperture ofsaid die being chamfered to obtain smooth coating or the strand, and the extrusion of coating material through said extrusion die being controlled bythe pressure of the coating material on the reduced center portion of said extrusion die.

4. In an apparatus for coating strand material. an extrusion chamber, a guiding die in said chamber, and an extrusion die of resilient material on the opposite sideot said chamber, said extrusion anextrusion chamber, a guiding die at one side of said chamber, and an extrusion die of resilient ing or the strand.

7 PETER J. KNAUS. 

